In this study, the photo-ozonation reaction for carbamazepine (CBZ) removal was investigated under alkaline conditions. Response surface methodology based on a central composite design was used to obtain the optimum experimental conditions, and examine both main and interaction effects of the photo-ozonation reaction variables such as O(3) concentration, H(2)O(2) concentration and UV intensity. The level of O(3) concentration significantly influenced CBZ removal (p < 0.001). CBZ removal increased with increasing both O(3) and H(2)O(2) concentration up to a certain level, whereas further increase in O(3) and H(2)O(2) concentration resulted in an adverse effect due to the hydroxyl radical scavenging effect. The optimum conditions for complete CBZ removal at pH 9 were found to be 0.89 mg of O(3) l(-1), 4.85 mg of H(2)O(2) l(-1) and 3.18 mW of UV intensity cm(-2), respectively.